Blade with tip rail cooling

ABSTRACT

An apparatus and method for cooling a blade tip for a turbine engine can include an blade, such as a cooled turbine blade, having a tip rail extending beyond a tip wall enclosing an interior for the blade at the tip. A plurality of film-holes can be provided in the tip rail. A flow of cooling fluid can be provided through the film-holes from the interior of the blade to cool the tip of the blade.

This application claims benefit of the filing date of and is adivisional of U.S. patent application Ser. No. 15/648,541, which isincorporated herein in its entirety.

TECHNICAL FIELD

This disclosure relates generally to a blade, and more specifically to ablade with tip rail cooling.

BACKGROUND OF THE INVENTION

Turbine engines, and particularly gas or combustion turbine engines, arerotary engines that extract energy from a flow of combusted gasespassing through the engine onto a multitude of rotating turbine blades,and in some cases, such as aircraft, generate thrust for propulsion.

Gas turbine engines for aircraft are designed to operate at hightemperatures to maximize engine efficiency, so cooling of certain enginecomponents, such as a high pressure turbine and a low pressure turbine,can be beneficial. Typically, cooling is accomplished by ducting coolerair from high and/or low pressure compressors to the engine componentsthat require cooling. Temperatures in the high pressure turbine can be1000° C. to 2000° C. and the cooling air from the compressor can be 500°C. to 700° C., enough of a difference to cool the high pressure turbine.

Contemporary turbine blades, as well as vanes or nozzles, generallyinclude one or more interior cooling circuits for routing the coolingair through the blade to cool different portions of the blade, and caninclude dedicated cooling circuits for cooling different portions of theblade, such as the leading edge, trailing edge and tip of the blade.

Turbine blade tip rails in particular help to reduce aero losses andtherefore increase the efficiency of turbine engines. The tip rail issubjected to a high heat loads and is difficult to effectively cool. Itis frequently one of the hottest regions in the blade.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, the disclosure relates to an airfoil comprising a bodydefining an interior, and extending axially between a leading edge and atrailing edge to defined a chord-wise direction and radially between aroot and a tip to define a span-wise direction, which terminates in atip end wall and a tip rail extending form the tip end wall, a coolingpassage formed in the interior, at least two circumferentially-spacedcooling cavities within the tip rail, the at least twocircumferentially-spaced cooling cavities spaced with respect to anexterior surface of the tip rail, a cooling conduit fluidly coupling thecooling passage with at least one of the at least twocircumferentially-spaced cooling cavities, a connecting conduit fluidlycoupling the circumferentially-spaced cooling cavities, and a film-holehaving an inlet fluidly coupled to at least one of thecircumferentially-spaced cooling cavities and an outlet provided on anexterior surface of the tip rail.

In another aspect, the disclosure relates to a blade for a turbineengine, the blade comprising a body defining an interior, and extendingaxially between a leading edge and a trailing edge to define achord-wise direction and radially between a root and a tip to define aspan-wise direction, with the tip terminating in a tip end wall, and atip rail extending from the tip end wall, at least one cooling passageformed in the interior, at least two circumferentially-spaced coolingcavities within the tip rail, the at least two circumferentially-spacedcooling cavities spaced with respect to an exterior surface of the tiprail, at least one cooling conduit fluidly coupling the cooling passagewith at least one of the at least two circumferentially-spaced coolingcavities, at least one connecting conduit fluidly coupling the coolingcavities, and a set of film-holes wherein each film-hole of the set offilm-holes includes an inlet fluidly coupled to at least one fo thecircumferentially-spaced cooling cavities and an outlet provided on atleast a portion of an exterior surface of the tip rail.

In yet another aspect, the disclosure relates to a method of cooling atip rail of an airfoil, with an internal cooling passage, for a turbineengine, the method comprising supplying cooling fluid to a first coolingcavity, located in the tip rail of the airfoil, through a first coolingconduit fluidly located within a wall of the airfoil and coupled to acooling passage, and supplying cooling fluid to a second cooling cavity,located in the top of the airfoil and spaced from the first coolingcavity, through a second cooling conduit fluidly coupled to the firstcooling cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional diagram of a portion of a turbineengine for an aircraft.

FIG. 2 is an isometric view of a blade for the engine of FIG. 1including a tip rail with cooling holes.

FIG. 3 is section view of the blade of FIG. 2 taken across sectionillustrating cooling passages within the blade.

FIG. 4 is a section view of the tip rail of the blade of FIG. 2 takenacross section IV-IV illustrating cooling cavities within the tip rail.

FIG. 5 is the section view from FIG. 4 illustrating a method of coolingthe tip rail of the blade of FIG. 2.

FIG. 6 is a section view of the tip rail of the blade of FIG. 2 takenacross section IV-IV illustrating cooling cavities within the tip railaccording to a second aspect of the disclosure described herein.

FIG. 7 is a section view of the tip rail of the airfoil of FIG. 2 takenacross section IV-IV illustrating cooling cavities within the tip railaccording to a third aspect of the disclosure described herein.

FIG. 8 is a is a section side view of the tip rail of the airfoil ofFIG. 2 taken across section VIII-VIII illustrating cooling cavitieswithin the tip rail according to a fourth aspect of the disclosuredescribed herein.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the disclosure described herein are directed to a tip of ablade including spaced cooling cavities having outlets formed in atleast a portion of a tip rail. For purposes of illustration, the presentdisclosure will be described with respect to a blade for a turbine in anaircraft gas turbine engine. It will be understood, however, thataspects of the disclosure described herein are not so limited and mayhave general applicability within an engine, including compressors, aswell as in non-aircraft applications, such as other mobile applicationsand non-mobile industrial, commercial, and residential applications.

As used herein, the term “forward” or “upstream” refers to moving in adirection toward the engine inlet, or a component being relativelycloser to the engine inlet as compared to another component. The term“aft” or “downstream” used in conjunction with “forward” or “upstream”refers to a direction toward the rear or outlet of the engine or beingrelatively closer to the engine outlet as compared to another component.

Additionally, as used herein, the terms “radial” or “radially” refer toa dimension extending between a center longitudinal axis of the engineand an outer engine circumference. A “set” as used herein can includeany number of a particular element, including only one.

All directional references (e.g., radial, axial, proximal, distal,upper, lower, upward, downward, left, right, lateral, front, back, top,bottom, above, below, vertical, horizontal, clockwise, counterclockwise,upstream, downstream, forward, aft, etc.) are only used foridentification purposes to aid the reader's understanding of the presentdisclosure, and do not create limitations, particularly as to theposition, orientation, or use of aspects of the disclosure describedherein. Connection references (e.g., attached, coupled, connected, andjoined) are to be construed broadly and can include intermediate membersbetween a collection of elements and relative movement between elementsunless otherwise indicated. As such, connection references do notnecessarily infer that two elements are directly connected and in fixedrelation to one another. The exemplary drawings are for purposes ofillustration only and the dimensions, positions, order and relativesizes reflected in the drawings attached hereto can vary.

FIG. 1 is a schematic cross-sectional diagram of a portion of a gasturbine engine 10 for an aircraft. The engine 10 has a longitudinallyextending axis or centerline 12 extending from forward 14 to aft 16. Theengine 10 includes, in downstream serial flow relationship, a fansection 18 including a fan 20, a compressor section 22 including abooster or low pressure (LP) compressor 24 and a high pressure (HP)compressor 26, a combustion section 28 including a combustor 30, aturbine section 32 including a HP turbine 34, and a LP turbine 36, andan exhaust section 38.

The fan section 18 includes a fan casing 40 surrounding the fan 20. Thefan 20 includes a plurality of fan blades 42 disposed radially about thecenterline 12 and rotatable within the fan casing 40. The HP compressor26, the combustor 30, and the HP turbine 34 form a core 44 of the engine10, which generates and extracts energy from combustion gases. The core44 is surrounded by core casing 46, which can be coupled with the fancasing 40.

A HP shaft or spool 48 disposed coaxially about the centerline 12 of theengine 10 drivingly connects the HP turbine 34 to the HP compressor 26.A LP shaft or spool 50, which is disposed coaxially about the centerline12 of the engine 10 within the larger diameter annular HP spool 48,drivingly connects the LP turbine 36 to the LP compressor 24 and fan 20.The spools 48, 50 are rotatable about the engine centerline and coupleto a plurality of rotatable elements, which can collectively define arotor 51.

The LP compressor 24 and the HP compressor 26 respectively include aplurality of compressor stages 52, 54, in which a set of compressorblades 56, 58 rotate relative to a corresponding set of staticcompressor vanes 60, 62 (also called a nozzle) to compress or pressurizethe stream of fluid passing through the stage. In a single compressorstage 52, 54, multiple compressor blades 56, 58 can be provided in aring and can extend radially outwardly relative to the centerline 12,from a blade platform to a blade tip, while the corresponding staticcompressor vanes 60, 62 are positioned upstream of and adjacent to therotating blades 56, 58. It is noted that the number of blades, vanes,and compressor stages shown in FIG. 1 were selected for illustrativepurposes only, and that other numbers are possible.

The blades 56, 58 for a stage of the compressor can be mounted to a disk61, which is mounted to the corresponding one of the HP and LP spools48, 50, with each stage having its own disk 61. The vanes 60, 62 for astage of the compressor can be mounted to the core casing 46 in acircumferential arrangement.

The HP turbine 34 and the LP turbine 36 respectively include a pluralityof turbine stages 64, 66, in which a set of turbine blades 68, 70 arerotated relative to a corresponding set of static turbine vanes 72, 74(also called a nozzle) to extract energy from the stream of fluidpassing through the stage. In a single turbine stage 64, 66, multipleturbine blades 68, 70 can be provided in a ring and can extend radiallyoutwardly relative to the centerline 12, from a blade platform to ablade tip, while the corresponding static turbine vanes 72, 74 arepositioned upstream of and adjacent to the rotating blades 68, 70. It isnoted that the number of blades, vanes, and turbine stages shown in FIG.1 were selected for illustrative purposes only, and that other numbersare possible.

The blades 68, 70 for a stage of the turbine can be mounted to a disk71, which is mounted to the corresponding one of the HP and LP spools48, 50, with each stage having a dedicated disk 71. The vanes 72, 74 fora stage of the compressor can be mounted to the core casing 46 in acircumferential arrangement.

Complementary to the rotor portion, the stationary portions of theengine 10, such as the static vanes 60, 62, 72, 74 among the compressorand turbine section 22, 32 are also referred to individually orcollectively as a stator 63. As such, the stator 63 can refer to thecombination of non-rotating elements throughout the engine 10.

In operation, the airflow exiting the fan section 18 is split such thata portion of the airflow is channeled into the LP compressor 24, whichthen supplies pressurized air 76 to the HP compressor 26, which furtherpressurizes the air. The pressurized air 76 from the HP compressor 26 ismixed with fuel in the combustor 30 and ignited, thereby generatingcombustion gases. Some work is extracted from these gases by the HPturbine 34, which drives the HP compressor 26. The combustion gases aredischarged into the LP turbine 36, which extracts additional work todrive the LP compressor 24, and are ultimately discharged from theengine 10 via the exhaust section 38. The driving of the LP turbine 36drives the LP spool 50 to rotate the fan 20 and the LP compressor 24.

A portion of pressurized airflow 76 generated in the compressor section22 can be drawn from the compressor section 22 as bleed air 77. Thebleed air 77 can be drawn from the pressurized airflow 76 and providedto engine components requiring cooling. The temperature of pressurizedairflow 76 entering the combustor 30 is significantly increased. Assuch, cooling provided by the bleed air 77 is necessary for operating ofsuch engine components in the heightened temperature environments.

A remaining portion of airflow 78 from the fan section 18 bypasses theLP compressor 24 and engine core 44 and exits the engine assembly 10through a stationary vane row, and more particularly an outlet guidevane assembly 80, comprising a plurality of airfoil guide vanes 82, at afan exhaust side 84. More specifically, a circumferential row ofradially extending airfoil guide vanes 82 is utilized adjacent the fansection 18 to exert some directional control of the airflow 78.

The airflow 78 can be a cooling fluid used for cooling of portions,especially hot portions, of the engine 10, and/or used to cool or powerother aspects of the aircraft. In the context of a turbine engine, thehot portions of the engine are normally downstream of the combustor 30,especially the turbine section 32, with the HP turbine 34 being thehottest portion as it is directly downstream of the combustion section28. Other sources of cooling fluid can be, but are not limited to, fluiddischarged from the LP compressor 24 or the HP compressor 26.

Referring to FIG. 2, an engine component in the form of one of theturbine blades 68 includes a dovetail 86 and an airfoil 88. The airfoil88 includes a tip 90 and a root 92 defining a span-wise direction therebetween. A tip wall 94 is provided at the tip 90, with a tip rail 96having an exterior surface 98 and extending from the tip wall 94 todefine a tip plenum 100. The airfoil 88 further includes a leading edge104 and a trailing edge 106 defining a chord-wise direction therebetween. A plurality of film-holes 112 are provided along a distal end111 of the tip rail 96 and can also be provided in the span-wisedirection along the trailing edge 106 of the airfoil 88. Furthermore, asecond set of film-holes 113 can be provided along the exterior surface98 of the tip rail 96.

The airfoil 88 mounts to the dovetail 86 by way of a platform 114 at theroot 92. The platform 114 helps to radially contain a turbine enginemainstream airflow driven by the blade 68. The dovetail 86 can beconfigured to mount to a turbine rotor disk on the engine 10 to drivethe blade 68. The dovetail 86 further includes at least one inletpassage 116, with the exemplary dovetail 86 shown as a having threeinlet passages 116. The inlet passages 116 extend through the dovetail86 and the platform 114 to provide internal fluid communication with theairfoil 88 at corresponding passage outlets 118. A flow of cooling fluidC, such as airflow 77 and/or airflow 78 can be provided to the airfoil88 through the inlet passage 116. It should be appreciated that thedovetail 86 is shown in cross-section, such that the inlet passages 116are enclosed within the body of the dovetail 86.

Referring now to FIG. 3, the airfoil 88 includes an outer wall 120 witha concave-shaped pressure side 122 and a convex-shaped suction side 124joined together to define the shape of airfoil 88. During operation, theairfoil 88 rotates in a direction such that the pressure side 122follows the suction side 124. Thus, as shown in FIG. 3, the airfoil 88would rotate upward toward the top of the page in the direction of arrow(A).

An interior 130 is defined by the outer wall 120. One or more interiorwalls shown as ribs 132 can divide the interior 130 into multiplecooling passages 119. Each of the passage outlets 118 can be fluidlycoupled to one or more internal cooling passages 119. The inlet passages116, passage outlets 118, internal cooling passages 119, and film-holes112, can be fluidly coupled to each other and form one or more coolingcircuits 121 within the airfoil 88.

It should be appreciated that the interior structure of the airfoil 88is exemplary as illustrated. The interior 130 of the airfoil 88 can beorganized in a myriad of different ways, and the cooling passages 119can include single passages extending in the span-wise direction, or canbe complex cooling circuits, having multiple features such as passages,channels, inlets, outlets, ribs, pin banks, circuits, sub-circuits,film-holes, plenums, mesh, turbulators, or otherwise in non-limitingexamples. Preferably, the cooling passages 119 will be in fluidcommunication with the inlet passages 116 of the dovetail 86. At leastone of the cooling passages 119 is in fluid communication with thefilm-holes 112.

As can be seen more clearly in FIG. 4, a cross-section of the tip rail96 taken across IV-IV of FIG. 2 shows a series 140 of spaced coolingcavities 140 a, 140 b, 140 c stacked within the tip rail 96 to define aportion of the cooling circuit 121 as described herein. In a firstaspect of the disclosure discussed herein, the spaced cooling cavitiesare radially-spaced cooling cavities 140 a, 140 b, 140 c. While threeradially-spaced cooling cavities 140 a, 140 b, 140 c are illustrated, atleast two are recommended, and it is further contemplated that four ormore are possible. A plurality of connecting conduits 142 a and 142 bcan fluidly couple the radially-spaced cooling cavities 140 a, 140 b,and 140 c to each other. It is contemplated that the connecting conduits142 a and 142 b can each having respective intermediate inlets 143 a,143 b and outlets 145 a, 145 b.

A cooling conduit 144 having an inlet 146 fluidly coupled to the coolingpassage 119 and an outlet 148 fluidly coupled to a first cooling cavity140 a connecting the series 140 of radially-spaced cooling cavities 140a, 140 b, 140 c to the cooling passage 119. It is contemplated that thecooling conduit 144 can be multiple cooling conduits 144 such that aplurality of cooling conduits 144 are formed between the cooling passage119 and at least one of the cooling cavities 140 a.

The plurality of film-holes 112 provided along the distal end 111 of thetip rail 96 can include a film-hole inlet 150 a fluidly coupled toradially-spaced cooling cavity 140 c and a film-hole outlet 152 afluidly coupled to an air source 154 surrounding the airfoil 88.

The second set of film-holes 113 provided along the exterior surface 98of the tip rail 96 can include a film-hole inlet 150 b fluidly coupledto radially-spaced cooling cavity 140 c and a film-hole outlet 152 bfluidly coupled to an air source 154 surrounding the airfoil 88 withinthe tip plenum 100.

It is further contemplated that the blade 68 can be located radiallybelow a shroud segment 156. The shroud segment 156 can be a plurality ofshroud segments 156 circumferentially arranged around the blades 68.

Turning to FIG. 5 a method of cooling the tip rail 96 of the airfoil 88is illustrated. Some numbers from FIG. 4 have been removed for clarity.The method includes supplying cooling air (C) through a series of theradially-spaced cooling cavities 140 a, 140 b, and 140 c in the tip rail96. The method can further include supplying the cooling air (C)sequentially first to cooling cavity 140 a, then cooling cavity 140 b,and finally cooling cavity 140 c. It is further contemplated that thesupplying can be provided to two or more cooling cavities 140 a, 140 b,and 140 c and is not limited to the three illustrated. It is furthercontemplated that the method can include impinging (I) the cooling fluid(C) onto the shroud segment 156 to cool the shroud segment 156.Likewise, it is further contemplated that the method can includeemitting the cooling fluid (C) through the outlet 152 b into the tipplenum 100 to cool the tip rail 96.

During operation it is contemplated that the tip rail 96 can contact theshroud segment 156 and over a lifetime of the blade 68 contact betweenthe tip rail 96 and the shroud segment 156 can cause rubbing away ofportions of the tip rail 96. Forming a series 140 of radially-spacedcooling cavities 140 a, 140 b, 140 c enables continued operation of theportion of the cooling circuit 121 having the radially-spaced coolingcavities 140 a and 140 b. In other words, as the tip rail 96 wears away,cooling cavity 140 b replaces cooling cavity 140 c in operation. In theevent cooling air (C) can no longer be provided to cooling cavity 140 c,the method simply includes providing cooling air (C) sequentially to afirst cooling cavity 140 a and then to the second cooling cavity 140 b.

FIG. 6 illustrates a series 240 of radially-spaced cooling cavities 240a, 240 b according to another aspect of the disclosure described herein.The series 240 of radially-spaced cooling cavities 240 a, 240 b hassimilarities to the series 140, therefore, like parts will be identifiedwith like numerals increased by 100. It should be understood that thedescription of the like parts of the series 140 apply to those of theseries 240, unless otherwise noted.

A cooling conduit 244 can have an inlet 246 fluidly coupled to a coolingpassage 219 and an outlet 248 fluidly coupled to a first cooling cavity240 a. The inlet 246 is spaced from the outlet 248 such that the coolingconduit 244 there between is angled with respect to a radial axis (R).The angled orientation of the cooling conduit 244 can be formed suchthat a portion (I) of cooling air (C) impinges on an interior surface260 of the cooling cavity 240 a before moving into a subsequent coolingcavity 240 b.

At least one connecting conduit 242 a can fluidly couple theradially-spaced cooling cavities 240 a and 240 b to each other. It iscontemplated that the connecting conduit 242 can extend from an inlet243 to an outlet 248 such that the cooling conduit 244 there between isangled with respect to the radial axis (R). The angled orientation ofthe connecting conduit 242 can be formed such that a portion (I) ofcooling air (C) impinges on an interior surface 260 of the coolingcavity 240 b before exhausting through a film-hole 212.

Turning to FIG. 7, it is further contemplated that the spaced cavitiesas discussed herein are circumferentially-spaced with respect to theengine centerline 12 rather than radially-spaced. A series 340 of spacedcooling cavities 340 a, 340 b has similarities to the series 140,therefore, like parts will be identified with like numerals increased by200. It should be understood that the description of the like parts ofthe series 140 apply to those of the series 340, unless otherwise noted.

In this aspect of the disclosure, a first cooling cavity 340 a iscircumferentially spaced from a second cooling cavity 340 b to definethe series 340. A cooling conduit 344 can have an inlet 346 fluidlycoupled to a cooling passage 319 and an outlet 348 fluidly coupled tothe first cooling cavity 340 a. A connecting conduit 342, illustrated asthree connecting conduits 342 a, 342 b, 342 c, can each extend from aninlet 343 a, 343 b, 343 c fluidly coupled to the first cooling cavity340 a to an outlet 345 a, 345 b, 345 c fluidly coupled to the secondcooling cavity 340 b.

At least one film-hole 312 can be along an outer wall 320 of tip rail296 and can include a film-hole inlet 350 fluidly coupled to the secondcooling cavity 340 b and a film-hole outlet 352 fluidly coupled to anair source 354 surrounding the airfoil 88.

The method as discussed herein can further include impinging (I) coolingfluid (C) both radially and circumferentially to maximize the amount ofheat removed by the cooling fluid (C). In this aspect of the disclosure,it is further contemplated that the method can also include emitting thecooling fluid (C) through the at least one film-hole 312 along the outerwall 320.

In yet another aspect of the disclosure discussed herein as depicted inFIG. 8 a side cross-section taken across VIII-VIII of FIG. 2 of the tiprail 96 with at least two radially-spaced cooling cavities 440 a, 440 b.The first set of cavities 440 a can include at least two first andsecond axially-spaced cavities 441 a, 441 b and the second set ofcavities 440 b, radially-spaced from the first set of cavities 440 a,can include third and fourth axially-spaced cavities 441 c, 441 d. Thefirst and second axially-spaced cavities 441 a, 441 b are radiallystacked below the third and fourth axially-spaced cavities 441 c, 441 dto define a series 440 of radially-spaced cooling cavities 440 a, 440 b.The series 440 has similarities to the series 140 therefore, like partswill be identified with like numerals increased by 300.

The first set of radially-spaced cavities 440 a can include a coolingconduit 444 having an inlet 446 fluidly coupled to a cooling passage 419and an outlet 448 fluidly coupled to a first axially-spaced cavity 441a. A first connecting conduit 442 a, oriented primarily in an axialdirection, can fluidly couple the first axially-spaced cavity 441 a tothe second axially-spaced cavity 441 b. A second connecting conduit 442b, oriented primarily in a radial direction, can fluidly couple thesecond axially-spaced cavity 441 b to the third axially-spaced cavity441 c. In doing so, the second connecting conduit 442 b couples thefirst set of radially-spaced cavities 440 a to the second set ofradially-spaced cavities 440 b. A third connecting conduit 442 c canfluidly couple the third axially-spaced cavity 441 c to the fourthaxially-spaced cavity 441 d. Film-holes 412 can fluidly couple thefourth axially-spaced cavity 441 d to an exterior air source 454. It isfurther contemplated that the second set of film-holes are connected toone or more of the cavities as illustrated, by way of non-limitingexample, in FIGS. 4, 6, and 7.

The method as discussed herein can further include impinging (I) coolingfluid (C) both radially and axially to maximize the amount of heatremoved by the cooling fluid (C).

While illustrated as four cavities, it should be understood that thedescription and orientation of the conduits, film-holes, and cavities asdescribed herein is for illustrative purposes and not meant to belimiting. For example each set of spaced cavities could include three ormore axially-spaced cavities each fluidly coupled to proximate coolingcavities. The arrangement of cooling cavities as illustrated in FIG. 8can be applied to the arrangements discussed regarding FIG. 4, FIG. 6and FIG. 7 or in any combination discussed herein.

Furthermore, the film-holes and second set of holes as discussed hereinare not limited to straight holes. Impingement holes can be curved orcan be angled, as illustrated in FIG. 6 to cool the sides of the tiprail.

The tip rail of the blade is subjected to high heat loads and frequentlyrubs against the shroud during operation. Designs accounting for theentire rail rubbing away during operation are necessary to continuecooling in this region as rub can remove cooling features or closecooling holes, completely cutting off coolant flow from this region. Asdiscussed herein a series of cavities spaced in the radial directionenables impingement cooling to be delivered directly to the top of therail, where a high demand for cooling exists. Additionally, if the topcavity rubs away, there is one below it to take its place in order tocontinue impingement cooling.

In the event that the rail rubs away and the top cooling hole closes,cooling flow can still be exhausted through the second set of holes,allowing the top of the rail to still be cooled. As more of the railrubs away, the top impingement cavity will completely open up and theone below it will take its place. In this way, a normal or near normallevel of cooling effectiveness can be maintained until the rail isalmost completely gone.

To the extent not already described, the different features andstructures of the various embodiments can be used in combination witheach other as desired. That one feature is not illustrated in all of theembodiments is not meant to be construed that it cannot be, but is donefor brevity of description. Thus, the various features of the differentembodiments can be mixed and matched as desired to form new embodiments,whether or not the new embodiments are expressly described. Allcombinations or permutations of features described herein are covered bythis disclosure.

It should be appreciated that application of the disclosed design is notlimited to turbine engines with fan and booster sections, but isapplicable to turbojets and turbo engines as well.

This written description uses examples to describe aspects of thedisclosure described herein, including the best mode, and also to enableany person skilled in the art to practice aspects of the disclosure,including making and using any devices or systems and performing anyincorporated methods. The patentable scope of aspects of the disclosureis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

What is claimed is:
 1. An airfoil comprising: a body defining aninterior, and extending axially between a leading edge and a trailingedge to define a chord-wise direction and radially between a root and atip to define a span-wise direction, which terminates in a tip end walland a tip rail extending form the tip end wall; a cooling passage formedin the interior; at least two circumferentially-spaced cooling cavitieswithin the tip rail, the at least two circumferentially-spaced coolingcavities spaced with respect to an exterior surface of the tip rail; acooling conduit fluidly coupling the cooling passage with at least oneof the at least two circumferentially-spaced cooling cavities; aconnecting conduit fluidly coupling the circumferentially-spaced coolingcavities; and a film-hole having an inlet fluidly coupled to at leastone of the circumferentially-spaced cooling cavities and an outletprovided on an exterior surface of the tip rail.
 2. The airfoil of claim1 wherein at least a portion of exterior surface of the tip rail definesa distal end of the tip rail.
 3. The airfoil of claim 2 wherein at leastanother portion of the exterior surface of the tip rail defines a tipplenum and a second set of film-holes are fluidly coupled to the tipplenum.
 4. The airfoil of claim 1 wherein the cooling conduit and theconnecting conduit are angled with respect to a circumferential axis. 5.The airfoil of claim 1 wherein the cooling conduit and the connectingconduit comprise multiple cooling conduits and multiple connectingconduits.
 6. The airfoil of claim 1 wherein the exterior surface of thetip rail is an outer surface of the tip rail.
 7. The airfoil of claim 1wherein the at least two circumferentially-spaced cooling cavitiescomprises three circumferentially-spaced cooling cavities.
 8. A bladefor a turbine engine, the blade comprising: a body defining an interior,and extending axially between a leading edge and a trailing edge todefine a chord-wise direction and radially between a root and a tip todefine a span-wise direction, with the tip terminating in a tip endwall, and a tip rail extending from the tip end wall; at least onecooling passage formed in the interior; at least twocircumferentially-spaced cooling cavities within the tip rail, the atleast two circumferentially-spaced cooling cavities spaced with respectto an exterior surface of the tip rail; at least one cooling conduitfluidly coupling the cooling passage with at least one of the at leasttwo circumferentially-spaced cooling cavities; at least one connectingconduit fluidly coupling the at least two circumferentially-spacedcooling cavities; and a set of film-holes; wherein each film-hole of theset of film-holes includes an inlet fluidly coupled to at least one ofthe circumferentially-spaced cooling cavities and an outlet provided onat least a portion of an exterior surface of the tip rail.
 9. The bladeof claim 8 wherein the exterior surface of the tip rail is a distal endof the tip rail.
 10. The blade of claim 9 wherein at least a portion ofthe exterior surface of the tip rail defines a tip plenum and a secondset of film-holes are fluidly coupled to the tip plenum.
 11. The bladeof claim 8 wherein the at least one cooling conduit and the at least oneconnecting conduit are angled with respect to a circumferential axis.12. The blade of claim 8 wherein the at least one cooling conduit andthe at least one connecting conduit comprise multiple cooling conduitsand multiple connecting conduits.
 13. The blade of claim 8 wherein theexterior surface of the tip rail is an outer surface of the tip rail.14. The blade of claim 8 wherein the at least twocircumferentially-spaced cooling cavities comprises threecircumferentially-spaced cooling cavities.
 15. A method of cooling a tiprail of an airfoil, with an internal cooling passage, for a turbineengine, the method comprising: supplying cooling fluid to a firstcooling cavity, located in the tip rail of the airfoil, through a firstcooling conduit fluidly located within a wall of the airfoil and coupledto a cooling passage; and supplying cooling fluid to a second coolingcavity, located in the top of the airfoil and spaced from the firstcooling cavity, through a second cooling conduit fluidly coupled to thefirst cooling cavity.
 16. The method of claim 15 wherein the supplyingthe cooling fluid comprises sequentially supplying cooling air to thefirst cooling cavity and the second cooling cavity.
 17. The method ofclaim 15 further including emitting the cooling fluid through an outletof a film-hole in the tip rail.
 18. The method of claim 15 furtherincluding further include emitting the cooling fluid through an outletof a film-hole which extends through at least a portion of an outer wallof the airfoil.
 19. The method of claim 15 further including impingingthe cooling fluid onto an interior surface of the first and secondcooling cavities.
 20. The method of claim 19 further including impingingthe cooling fluid onto a radial and an axial surface of the first andsecond cooling cavities.